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HART Multi-Drop Connection Wiring
HART Transmitters in Multidrop wiring

Dear All,

We are evaluating and testing the mechanism to connect 7 HART Flow meters to a single Master to gather process Information. We are aware of HART Multimode wiring is possible and that we can connect the 7 flow Meters in a daisy chain fashion.

It will be really helpful to get some advice on wiring aspect for this daisy chain from someone who has already done such kind of HART multidrop Interface (which is not very usual).

I checked some online information - which dictates to introduce an external power supply in the multidrop wiring - we need to know how is this wiring done.

Please note the Flow Meter detail:
E&H, Promag 400 - flow meters. requires external 110VAC supply.

Please note the single HART master/converter detail:
Moore Industry HCS Module.

Thanks a lot for your advice and support.
Regards,
Tom

1. It might help to take a look at the HCS installation manual. It is available here:
http://www.miinet.com/Portals/0/Manuals/HCS_Installation_Manual_Moore_Industries.pdf

Page 6 shows the HCS powering the multidrop network.
Page 7 shows an external power supply powering the network.

Pretty straightforward.

2. Are you aware of the inherent slow response of a multidrop HART network?

quote from the manual:
Digital Response Time:
Equals the combination of the HART response time and the MODBUS response time; the HART delay is defined by the HART protocol as 500msec in normal mode and 333msec in burst mode; the MODBUS response time depends on how fast and how often a MODBUS Master requests data from the HCS; the data request to response time is 50msec.

That's about 2.5+ to almost 4 seconds to an update from 7 instruments, depending.